Buoy level gauge does not belong to special equipment. The state cancelled the administrative license of special equipment for buoy level meter, which is not a special equipment. Buoy level gauge is a liquid level measuring instrument designed according to Archimedes principle and magnetic coupling principle. The instrument can be used to measure liquid level, boundary position and density, and is responsible for outputting upper and lower limit alarm signals. It is specially used to measure the liquid level in pressure vessels.